undo

An undo-redo library.

An implementation of the command pattern. Each modification to a target value is represented as a struct that knows how to apply itself and how to reverse the change. The provided data structures wrap these commands and give you linear or tree-shaped undo-redo navigation over any target type.

Features

• Linear undo-redo with Record or full branching history with History
• Merge consecutive edits into a single undo step
• Mark the target as saved and receive notifications when that state changes
• Cap the undo stack to retain only the N most recent edits
• Batch edits with a queue, or apply tentative edits with a checkpoint
• Colored and configurable display formatting
• no_std compatible via the alloc feature
• Optional serde support

Example

use undo::{Edit, Record};

struct Add(char);

impl Edit for Add {
    type Target = String;
    type Output = ();

    fn edit(&mut self, target: &mut String) {
        target.push(self.0);
    }

    fn undo(&mut self, target: &mut String) {
        self.0 = target.pop().unwrap();
    }
}

fn main() {
    let mut target = String::new();
    let mut record = Record::new();

    record.edit(&mut target, Add('a'));
    record.edit(&mut target, Add('b'));
    record.edit(&mut target, Add('c'));
    assert_eq!(target, "abc");

    record.undo(&mut target);
    record.undo(&mut target);
    record.undo(&mut target);
    assert_eq!(target, "");

    record.redo(&mut target);
    record.redo(&mut target);
    record.redo(&mut target);
    assert_eq!(target, "abc");
}

Record vs History

Use Record for a simple linear undo stack. Applying a new edit after undoing discards the now-unreachable edits. Use History when you need a full undo tree: undoing and then making a new edit creates a branch, and you can navigate back to any prior state at any time.

See the documentation and examples for more information.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.